1. Field of the Invention
The present invention relates to an exposure control apparatus, and more particularly to an exposure control apparatus which controls exposure by an output of a sensor which detects a focus state of an imaging lens.
2. Description of the Prior Art
A prior art apparatus having a focus detection apparatus uses an exposure control sensor and a focus detection sensor independently, because desired output forms of the sensors are different. The output of the exposure control sensor must change with a change of brilliance of an object. On the other hand, in the focus detection sensor, outputs of elements of the sensor are compared or differentiated. Accordingly, variation of the output levels of the elements causes a detection error. Thus, the outputs must be constant even if the brilliance of the object changes. When storage type photosensing elements are used in the focus detection sensor, a storage time of a signal from a photoelectric converter is changed with a change of the brilliance of the object so that a constant output is always produced.
The focus detection sensor comprises a number of picture cells. Since each picture cell is much smaller than the exposure control sensor, the output from each picture cell cannot be used as a measurement for the exposure control.
Accordingly, in the prior art camera, the exposure control sensor and the focus detection sensor must be separately provided. This causes a structure to be complex and increases its size.